Method of grinding



May 22, i923. 'mjl' s. EINSTEIN METHOD OF GRINDI NG Filed Aug. 17, 1925 Patented Mayy 22, 192s.'

UNITED STATES SOL EINSTEIN, OF CINCINNATI, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

PATENT OFFICE.

CIN-

CINNATI GRINDERS INCORPORATED, OF CINCINNATI, OHIO, A.' CORPORATION OF OHIO.

l 1 METHOD OF GRINDING.

Application led August 17, 1925. Serial No. 50,738. i

This invention relates to abrading and particularly to a method of centerless grinding. By the term centerless grinding I mean the production of surfaces of rotation 5 by the coaction of a grinding wheel and an opposed regulating wheel without mounting the work piece on centers.

A centerless grinder consists of two wheels, preferably both of abrasive material, one of which, the grinding wheel, runs at such high speed that it performs an abrading function, and the other of which, the regulating wheel, runs at such a relatively low speed that it performs virtually 11o 15 abrading function, but regulates the rotation of the .work and also, in certain cases, feeds the work axially.. The work is supported between the wheels'by a work rest which preferably is so positioned that itv sustains the work with its axis above a line connectingthe centers of the grinding and regulating wheels, and is so incline that the work piece tends to move under` the action of gravity into contact with the regulating wheel. At the work rest the grinding wheellsurface moves downward or toward the Workrest, and thus urges the work piece against the work rest. The regulating wheel moves at the work rest upward or away from the work rest, and regulates the rotation of the work.

There are two types of centerless grinder now coming into extensive use. The more common and simpler type is known as\the through-feed grinder. In this type of grinder the regulating wheel is so mounted that it imparts to the work piece a component of motion in the direction of'its axis. IVherethe wheels are peripherally opposed, 40 -this effect is secured by slightly skewing the regulating wheel. The work. pieces are fed to the work rest axially or end to end by any suitable means, for example, by an inclined trough or chute. They enter be- E tween the wheels, and are fed by the regulating wheel successively between the wheels in the direction of their axes. This type of machine is particularly adapted for grindextensively used for that purpose.

The through-feed grinder is not generally adapted, however, for shouldered pieces and tapered pieces, and to grind such 4pieces another type of centerless' grinder has been ing straight cylindrical pieces and has been only a sively devised and may be designated as an infeed grinder. In the in-feed grinder the entire length of the surface to be ground is in contact with the abrading surface of the grinding wheel throughout the grinding operation, and the piece is not yfed between the wheels'axially, but is inserted between the wheels. This is commonly done while the latter are slightly withdrawn from each other,but such separation is not always necessary. After insertion lof the work piece, the wheels if they have beenl separated are fed in, i. e., moved automatically or manually towardv each other until they are spaced apart a definite distance. At the end of such, feedin in the piece is yallowed to run a short tlme for finish. yWhen the grinding has been completed the work piece is ejected. This may be done without separation of the wheels, or after the wheels have been slightly separated to release it.

d In such grinding the grinding wheel may be oscillated slightly in an axial direction to 1 distribute the wear on lthe -wheel and assure the retention of its true surface.

As stated, the in-feed machine was devised primarily for the purpose of acting on those orms of work blank which are not susceptible of being fed axially between the wheels, but I have discovered by experimentation and tests that the operative characteristics of the two types of machine are inherentl different, and that, for cert-ain classes o work, they are complementary to each other and may be conjointly used for the commercial production of finished pieces which cannot be so well produced, or which cannot be so economically produced, by,

either machine alone.

The in-feed grinder can be used to remove i a larger amount of metal than can the through-feed grinder. fed, the cut may be made progressively in a radial direction and a relatively deepcut can be effected gradually. Operating on a work blank which is out of round orgslightlyl tapered the in-feed grinder, when proper- If the wheels are l ly adjusted, has an inherent tendency to re f duce that work blank to true cylindrical' form. The through-feed grinder can make of round is limited cut and makes this progres,

While in-feed grinding is capable of producing linished'pieces of the utmost accuracy, it is obvious that if this grinder be used to remove a considerable amount of metal its precision Will necessarily be impaire during the product-ion of a relatively .small number of pieces. If the machine be required merely to perform a rough-grinding operation, the product can be held quite easily Within the limits necessary for roughl grinding, and the rough-ground product will be true in form and susceptible of successful finish-grinding in a through-feed grinder.

My process, therefore, in the best form knownto me contemplates rough-grinding the blank by thein-feed method, that is, by placing it betweenthe Wheels in position to Contact With the grinding Wheel throughout its entire length and then moving the Wheels one toward the other until there is a definite linterval between the Wheels, the grinding being eected as the wheels approach eachl other. At the termination of this operation, the Wheels are separated and the roughground piece is ejected. This rough-grinding operation not only brings the piece approximately to size, but brings it to a truly round and truly cylindrical form. The resulting rough-ground piece is then in an ideal condition for finishing by the throughl'feed method, and since the through-feed method is much faster, requires far lesssupervision, and can be carried out With a much less expensive machine, the final step of finish-grinding by the through-feed process offers many commercial advantages.

operation starting with .a truly cylindrical blank 1s an operation of the utmost precision because the blank moves across the face of both Wheels and the finished diameter of the grinding wheel and regulating wheel are indicated by arrows, while the opposed f arrows 5 indicate diagrammatically that the woutthe relation of the lWork rest and the' v regulating wheel is fed toward and from the grinding wheel.

The above grinding elements arey illustrated in side elevation.v The grindingelements of the through-feed grinder are illustrated in edge elevation in order to bring skewing-of the regulatingyvheel. 'The4 rinding wheel is illustrated-at 6, the regu ating wheel at 7, and the Work rest at 8. Work pieces 4, after ejection from between the Wheels 1 and 2, are fed to the Wheels 6 and 7 by means of an inclined trough 9 which discharges them upon the Work rest 8 in position to be gripped by thevvhcels 6 and 7 and fed axially between the Wheels. During movement between the Wheels the Work piece is rotated, the Wheel 7 regulating the rotation and the feed and the Wheel 6 performing an abrading action, so that the finished work pieces discharge from the machine down a chute or trough 10.

y While a single finish-grinding operation is ordinarily suiicient, I illustrate in the drawing-the'possibility of using more than one such finish-grinding operation. The second finish-grinding is vconducted in a through-feed grinder consisting of a grind- `ing Wheel 11, regulating Wheel 12, and Workrest '13. The Work pieces from the discharge trough 10 of the firstthrough-feed grinder are supplied to the feed trough 14 of the second through-feed grinder which directs them to the work rest 13. From the Work rest 13 they are discharged by means of a chute 15. In cases Where the utmost precision is desired a series of finish-grinding operations may be used, the machines being so adjusted that each successive machine removes less stock thanits predecessor.V In this Way the grinding Wheel of the last finish-grinding machine is subjected to the minimum Wear and its precision is thus maintained unimpaired for a longer period of operation. Furthermore, a through-feed grinding" While I suggest the use of separate machines, it should be appreciated that a single centerless grinder can be set up to operate either on the in-feed principle or onthe through-feed principle. This being the case, it is obviously practicable to set the 'same machine up for the rough-grinding operations on the in-feed' principle and then, after a suiiicient quantity of rough-ground blanks has been produced, to set up the same Ina-` 'chine to operate on the through-feed principle and use A'it to fnishrind these same blanks; Hence I. do not implyany necessary limitation to the use of distinct machine-s, .the invention residinor in the steps of the vprocessand the order 1n which these steps are performed rather than in the particular machine or machinesused to perform lil'lel'n.4 i i The process takes advantage. of the best features of both types of grinding. Starting with an over-sized blank of inaccurate form, it reduces this blank.' to accurate form with very slight over-size.'4 The roughground blankthus produeedis then peculiar- 1y susceptible to successfulnish' by the through-.feed grinding process. and the'fnal product is of the utmost precision. In this way it is possible to produce on a commercial s cale a finished product which surpasses in quality that heretofore produced by centerless grinding methods, notwithstanding the fact that those methods far exceeded the' precision of any known method of grinding on centers. In fact, conventional centerless grinding methods have enabled manufacturers in the lmotor car industry to increase their production rate, reduce their production costs, and at the same time produce a linished product with plus and minus tolerances one-fourth those customarily sety for the highest grade of work by the center grinding method. The present method is a further advance in the same direction.

`What I claim is:

l. That method of producing a finished cylindrical work piece by centerless grinding which consists in rough-grinding a blank by the centerless in'feed method and there-V after finish-grinding said blank by the through-feed benterless grinding method.

2. That method of producing a finished cylindrical work pieceby centerless vrinding which consists in rough-grinding abblank by supporting it on a work rest between a regulating wheel and a grinding wheel running at appropriate speeds, and then feeding said wheels one toward the other until a definite interval is presented between said wheels, and finally feeding said blank axially upon a work rest between and beyond opposed regulating andl grinding wheels spaced appropriate fixed distances apart to effect the desired finishing cut, said wheels beingv driven at appropriate differential speeds.

' 3. That method of producing finished cylindrical work pieces by centerless grinding which .consists in rough-grinding a blank' by the in-feed centerless method and thereby rendering it truly cylindrical and reducing its size by a substantial amount to a diameter slightly in excess of the desired iinished diameter, and then finish-grinding said blank by one or more finish-grinding operations conducted by the centerless through-feed method.

s 4. That method of producing finished cylindrical work pieces by centerless grinding which consists in rough-grinding a blank bythe in-feed centerless method whereby the diameter of the blank is reduced a `subs tantial amount' to a diameter slightly in soL EINSTEIN. 

